1. Technical Field
The present invention relates to an infrared sensor package which detects infrared radiation using by an infrared detection element which is vacuum-sealed within the package.
2. Background Art
In recent years, on a package in which an infrared sensor is vacuum-sealed or an electronic apparatus equipped with the package, there are demands for miniaturization, performance improvement and cost reduction. Quantum-type and thermal-type infrared sensors are mentioned as general infrared sensors. The thermal-type one uses a method of detecting relative amount of heat, so it can be operated in an uncooled system and be simple in structure. Accordingly, the thermal-type one can be produced at lower cost than the quantum-type one, while the former is inferior to the latter in tracking performance.
A thermal-type infrared sensor package is disclosed, for example, in Patent document 1 (Japanese Patent Application Laid-Open No. H06-137940), Patent document 2 (Japanese Patent Publication No. H07-508384) and Patent document 3 (Japanese Patent Application Laid-Open No. 2006-081204). A cross-section structure of an infrared sensor of Patent document 1 is shown in FIG. 12. In an infrared sensor package 900 of Patent document 1 shown in FIG. 12, a substrate 920 in which a hollow space portion is formed is disposed on a base plate 910. There are laminated a heat-insulating film 930, heating element 940 and infrared detection element 950 on the substrate 920. Further, a cap 960 including a filter window 961 is disposed above the infrared detection element 950. The infrared sensor package 900 is formed by forming space which is maintained at reduced pressure using the cap 960 and base plate 910.
Thus disposing an infrared detection element 950 within the space maintained at reduced pressure, it is possible to reduce the amount of heat escaping through the air from the infrared detection element 950, and thus to improve the sensitivity of the infrared sensor package 900.
Further, in the infrared sensor package 900 of Patent document 1, the heating element 940 and the base plate 910 are thermally separated from each other by the formation of a hollow space portion underneath the infrared detection element 950 on the substrate 920, and the heat-insulating film 930 is disposed between the heating element 940 and the substrate 920. In this way, outflow of the heat to the substrate 920 is suppressed.
On the other hand, Patent document 2 discloses an infrared sensor package provided with a Pelletier element which is used as a thermoelectric temperature stabilizer in order to keep the temperature of the infrared sensor element constant.